JP6262140B2 - Method for producing metal plate having alloy plating layer - Google Patents

Description

  The present invention relates to a method for producing a metal plate having an alloy plating layer.

  Conventionally, a method is known in which an alloy plating layer containing nickel, cobalt, or the like is formed on a metal plate such as a steel plate by electroplating (see, for example, Patent Document 1).

WO1997 / 042667

  As a method for industrially producing a metal plate having such an alloy plating layer, a method in which a metal strip is continuously supplied into a plating tank and electroplating is continuously performed in the plating tank is common. According to such a method, the alloy plating layer can be continuously formed on the metal strip. However, on the other hand, in such a method, in order to make the composition of the alloy plating layer obtained by continuously forming the alloy plating layer constant, metal ions in the plating solution contained in the plating tank are used. It is necessary to suppress fluctuations in concentration.

  As a method of suppressing fluctuations in the concentration of metal ions in the plating solution contained in the plating tank, for example, metal salt compound powder is added to the plating solution to compensate for metal ions consumed by forming an alloy plating layer. And the method of making it melt | dissolve in a plating solution is mentioned. However, in this method, it is difficult to continuously add powder, and when a liquid in which powder is preliminarily dissolved in water is continuously added, water also enters the plating solution at the same time. When suppressing fluctuations, it is necessary to make adjustments that take into account the balance of the liquid volume. Although it is possible to compensate for the consumed metal ions, the addition of the metal salt compound powder increases the counter anion in the plating solution, resulting in the composition of the intended alloy plating layer. There is a problem that the characteristics cannot be obtained. Furthermore, since such a metal salt compound powder is generally expensive, there is a problem that the manufacturing cost becomes high.

  Further, as another method for suppressing the fluctuation of the metal ion concentration in the plating solution contained in the plating tank, a method using an anode made of each metal constituting the alloy plating layer as the anode (anode) can be considered. That is, the case of forming a nickel-cobalt alloy plating layer is exemplified by a method in which a nickel electrode and a cobalt electrode are used as an anode, and these are used as a supply source of nickel ions and cobalt ions. However, according to this method, the ratio of nickel ions and cobalt ions supplied from these electrodes is determined according to the number of nickel electrodes and cobalt electrodes, so that only an alloy plating layer having a specific ratio can be formed. There's a problem. Further, in this method, a plurality of anodes are used, and it is necessary to control the current for each anode. However, it is very difficult to keep the current flowing uniformly through each anode. There is also a problem that it cannot be formed stably.

  Furthermore, as another method for suppressing the fluctuation of the metal ion concentration in the plating solution contained in the plating tank, a method of using an alloy pellet made of an alloy of each metal constituting the alloy plating layer as an anode (anode) is also conceivable. However, it is not easy to produce a pellet made of an alloy, and it is extremely difficult to produce an alloy pellet containing a metal having a particularly high melting point. In the method using alloy pellets, it is necessary to use alloy pellets having a composition ratio corresponding to the target alloy plating layer. In this case, depending on the metal ratio of the target alloy plating layer, the alloy pellets are used. There is a problem that it is necessary to prepare the alloy plating layer, and when the target alloy plating layer is changed, all the alloy pellets filled in the anode basket must be replaced. Furthermore, in the method using alloy pellets, depending on the type of metal constituting the alloy pellets, the ratio of each metal dissolved from the alloy pellets (dissolution ratio) may not be stable, and the desired alloy plating layer is formed. There is also a problem that it cannot be done.

  The present invention has been made in view of such a situation, the purpose of which, when producing a metal plate having an alloy plating layer, it is possible to suppress the fluctuation of the metal ion concentration in the plating solution contained in the plating tank, Thereby, it is providing the manufacturing method of the metal plate which has an alloy plating layer which can stabilize the composition of the alloy plating layer obtained.

As a result of intensive investigations to achieve the above object, the present inventors have continuously provided a metal strip in a plating tank comprising a plating solution containing two or more kinds of metal ions for forming an alloy plating layer and an anode. When performing electroplating in a plating tank by passing the plate, an anode formed by mixing two or more kinds of metal pellets for forming an alloy plating layer is used as the anode, and the total surface area of each metal pellet By controlling the ratio, the dissolution ratio of each metal pellet constituting the anode is made constant, and further, when performing electroplating, the anode is replenished with metal pellets at a predetermined ratio. The inventors have found that the above object can be achieved by suppressing fluctuations in the concentration of metal ions in the liquid, and have completed the present invention. In addition, in this invention, each metal pellet shows the metal pellet which consists of each metal.

That is, according to the present invention, there is provided a method for producing a metal plate having an alloy plating layer, the plating tank comprising a plating solution containing two or more kinds of metal ions for forming the alloy plating layer, and an anode. An anode formed by mixing two or more kinds of metal pellets made of each metal forming the alloy plating layer as the anode, comprising a step of continuously passing a metal strip and performing electroplating in the plating tank And the total surface area ratio of each metal pellet in the anode is such that the dissolution ratio of each metal pellet constituting the anode is a dissolution ratio corresponding to the weight ratio of each metal constituting the alloy plating layer. based on the mixing ratio determined for each metal pellets constituting the anode, when performing electroplating in the plating bath, the metal pellets in the anode Definitive when refilling, replenishing ratio of the metal pellets, method for producing a metal plate having an alloy plated layer, characterized in that the ratio corresponding to the weight ratio of each metal constituting the alloy plating layer is provided .

In the manufacturing method of the present invention, each metal forming the alloy plating layer is M ₁ , M ₂ , M ₃ ,... M _n, and the dissolution ratio of each metal pellet constituting the anode (unit:% ) Is y (M ₁ ), y (M ₂ ), y (M ₃ ),..., Y (M _n ), and the weight ratio of each metal constituting the alloy plating layer (unit:%) , Z (M ₁ ), z (M ₂ ), z (M ₃ ),..., Z (M _n ), the dissolution ratio of each metal pellet constituting the anode is determined by the alloy plating. M ₁ , M ₂ , M ₃ ,... M _n with respect to the weight ratio of each metal constituting the layer, the metal pellets in the anode satisfying the relationship of the following formula (1) Based on the total surface area ratio, the mixing ratio of each metal pellet constituting the anode is determined. It can be configured.
z (M _x ) −21 ≦ y (M _x ) ≦ z (M _x ) +21 (1)
(In the above formula (1), M _x represents M ₁ , M ₂ , M ₃ ,... M _n , respectively.)

In the production method of the present invention, each metal pellet having a representative length of 5 to 50 mm and a volume of 60 to 5000 mm ³ can be used.
In the manufacturing method of the present invention, the alloy plating layer may be a nickel-cobalt alloy plating layer, and the anode may be an anode formed by mixing nickel pellets and cobalt pellets. .
Furthermore, in the production method of the present invention, z (Co) which is a weight ratio (unit:%) of cobalt in the alloy plating layer is set to 40 ≦ z (Co) ≦ 60, and the total surface area ratio of the cobalt pellets X (Co) which is (unit is%) is the following formula in relation to z (Co) and y (Co) which is the dissolution ratio (unit is%) of the cobalt pellet constituting the anode. (2) It can comprise so that the mixing ratio of the said nickel pellet and the said cobalt pellet which comprises the said anode may be determined so that (3) may be satisfy | filled.
z (Co) -21 ≦ y (Co) ≦ z (Co) +21 (2)
y (Co) = − 0.8x (Co) ² + 1.8x (Co) (3)

  According to the present invention, when manufacturing a metal plate having an alloy plating layer, an anode formed by mixing two or more metal pellets for forming the alloy plating layer is used as an anode used for electroplating. And by controlling the total surface area ratio of each metal pellet, fluctuations in the metal ion concentration in the plating solution contained in the plating tank can be suppressed, thereby stabilizing the composition of the resulting alloy plating layer. it can.

FIG. 1 is a diagram illustrating an example of a plating line used in the present embodiment. FIG. 2 is a diagram for explaining a plating method according to a conventional example. FIG. 3 is a diagram for explaining a plating method according to a conventional example. FIG. 4 is a diagram for explaining a plating method according to a conventional example. FIG. 5 is a diagram for explaining a plating method according to a conventional example. FIG. 6 is a diagram showing measurement results of the amount of nickel ions and the amount of cobalt ions in the examples in the plating process. FIG. 7 is a diagram showing measurement results of the amount of nickel ions and the amount of cobalt ions in the comparative example. FIG. 8 is a diagram showing the relationship between the cobalt mixing ratio (surface area ratio) in the anodes 70a to 70d and the cobalt dissolution ratio (weight ratio) in the examples and comparative examples.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a plating line used in the present embodiment. The plating line of this embodiment is a line for forming an alloy plating layer on the metal strip 10, and the metal strip 10 is provided with a plating solution 30 by a conductor roll 40 as shown in FIG. The alloy plating layer is continuously formed on the metal strip 10 by being continuously fed into 20 and electroplated in the plating tank 20.

  As shown in FIG. 1, the plating line of this embodiment includes a conductor roll 40 for transporting the metal strip 10 into the plating bath 20, and a sink roll for changing the traveling direction of the metal strip 10 in the plating bath 20. 50, a conductor roll 60 for lifting the metal strip 10 from the plating tank 20 is provided. In the present embodiment, among these rolls, the conductor rolls 40 and 60 are electrically connected to the rectifiers 80a and 80b so that a cathode current is supplied from an external power source (not shown) via the rectifier. It has become. As a result, a direct current is applied to the metal strip 10 from the external power source via the conductor rolls 40 and 60.

  In addition, four anodes 70a to 70d are immersed in the plating tank 20, and among the four anodes 70a to 70d, the anodes 70a and 70d are electrically connected to the rectifier 80a. The anodes 70b and 70c are electrically connected to the rectifier 80b, and an anode current is supplied from an external power source (not shown) through the rectifiers 80a and 80b.

  Therefore, the metal strip 10 is energized by the action of the conductor rolls 40 and 60, and is transported into the plating solution 30 in the plating tank 20 in the energized state, whereby the alloy plating is performed by the action of the four anodes 70a to 70d. The alloy plating layer is formed on the metal strip 10.

  In the present embodiment, the metal strip 10 is not particularly limited. For example, the steel strip, tin-free steel, aluminum alloy plate, galvanized steel plate, zinc-cobalt-molybdenum composite plated steel plate, zinc-nickel alloy plated steel plate, zinc- Various metals such as iron alloy-plated steel sheet, galvannealed steel sheet, zinc-aluminum alloy-plated steel sheet, zinc-aluminum-magnesium alloy-plated steel sheet, nickel-plated steel sheet, copper-plated steel sheet, and stainless steel sheet can be used.

  Moreover, in this embodiment, it does not specifically limit as an alloy plating layer formed on the metal strip 10, For example, the availability as a metal pellet for anode 70a-70d formation mentioned later, and stability of this metal pellet From the standpoint of properties, nickel-cobalt alloy plating layer, nickel-tin alloy plating layer, nickel-zinc alloy plating layer, copper-nickel alloy plating layer, tin-zinc alloy plating layer, tin-copper alloy plating layer, tin- Examples include a cobalt alloy plating layer, a copper-zinc alloy plating layer, and a copper-cobalt alloy plating layer. Among these, a nickel-cobalt alloy plating layer is preferable because high conductivity can be secured when used for battery containers. The nickel-cobalt alloy plating layer preferably has a cobalt content (z (Co)) in the range of 40 to 60% by weight (40 ≦ z (Co) ≦ 60). By setting the content ratio of cobalt within the above range, high conductivity can be ensured while preventing elution of cobalt into the electrolyte when used for battery containers.

  What is necessary is just to use the thing according to the kind of alloy plating layer formed on the metal strip 10, and an alloy composition as the plating solution 30, Usually, each metal which comprises the alloy plating layer formed on the metal strip 10 is used. Those containing ions are used. For example, when the alloy plating layer formed on the metal strip 10 is a nickel-cobalt alloy plating layer, a Watt bath containing nickel sulfate, nickel chloride, cobalt sulfate and boric acid is used as the plating solution 30. A base plating bath or the like can be used. In addition, the compounding quantity in this case shall be the range of nickel sulfate: 10-300g / L, nickel chloride: 20-60g / L, cobalt sulfate: 10-250g / L, boric acid: 10-40g / L, for example. Can do. In the present embodiment, as the plating solution 30, a larger amount of plating solution than the capacity of the plating tank 20 is prepared, and a part of the prepared plating solution 30 is installed outside the plating tank 20. It may be placed in a tank (not shown) and the electrolytic treatment may be performed while circulating between the plating solution tank and the plating tank 20 by a pump or the like.

In this embodiment, the anodes 70a to 70d are formed by mixing two or more kinds of metal pellets for forming an alloy plating layer on the metal strip 10. That is, for example, when the alloy plating layer formed on the metal strip 10 is an alloy of two kinds of metals, M ₁ metal and M ₂ metal, M ₁ metal pellets and M ₂ metal A mixture of pellets is used. Details of the anodes 70a to 70d will be described later.

  The rectifiers 80a and 80b are not particularly limited, and a known rectifier can be used according to the magnitude and voltage of the current supplied to the conductor rolls 40 and 60 and the anodes 70a to 70d.

  In the present embodiment, electroplating is performed on the metal strip 10 and alloy plating is formed on the metal strip 10 as follows.

  That is, first, the metal strip 10 is transported into the plating tank 20 by the conductor roll 40, and is transported between the anodes 70 a and 70 b immersed in the plating solution 30 in the plating solution 30 of the plating tank 20. The metal strip 10 is opposed to the anodes 70a and 70b when passing between the anodes 70a and 70b, and is electroplated by the action of a direct current applied from an external power source through the energized conductor rolls 40 and 60. An alloy plating layer is formed.

  Next, the metal strip 10 is subjected to electroplating by the action of the anodes 70a and 70b, then the direction of travel is changed by the sink roll 50, and then conveyed between the anodes 70c and 70d immersed in the plating solution 30. The The metal strip 10 faces the anodes 70c and 70d when passing between the anodes 70c and 70d, and is electroplated by the action of a direct current applied from an external power source through the energized conductor rolls 40 and 60. Further formation of the alloy plating layer is performed. Next, the metal strip 10 is pulled up by the conductor roll 60. In the present embodiment, an alloy plating layer is formed on the metal strip 10 in this way.

  In FIG. 1, only the plating tank 20 is shown as a plating line used in the present embodiment, but before the electroplating is performed in the plating tank 20, a degreasing treatment tank for degreasing the metal strip 10. And a degreasing liquid rinsing bath, a pickling bath for pickling, and a pickling rinsing bath. In this case, the metal strip 10 is conveyed to the degreasing treatment tank and degreased, and then conveyed to the degreasing liquid rinsing treatment tank, and the degreasing treatment liquid is washed away in the degreasing liquid rinsing tank. Furthermore, after being pickled in the pickling treatment tank and pickling in the pickling treatment tank, it is transported to the pickling solution rinsing treatment tank, and the pickling solution is washed away in the pickling solution rinsing treatment tank. And it is conveyed to the plating tank 20 and electroplating will be performed in the plating tank 20.

  Moreover, in this embodiment, after the electroplating is performed in the plating tank 20 after the pretreatment such as strike plating before the electroplating is performed in the plating tank 20, An electrolytic solution rinsing treatment tank for washing away the plating treatment solution 30 adhering to the belt 10 may be further provided.

  Further, FIG. 1 illustrates a configuration having one plating tank 20, but it is assumed that a plurality of plating tanks 20 are continuously provided according to the thickness of the alloy plating layer formed on the metal strip 10. It is good also as a simple structure.

Next, the anodes 70a to 70d used in the present embodiment will be described in detail. In the present embodiment, the anodes 70 a to 70 d are formed by mixing two or more kinds of metal pellets for forming an alloy plating layer on the metal strip 10. Specifically, when the alloy plating layer is two metals of alloys of the metal M ₁ of a metal, M ₂ is a pellet of a metal M _1, and a metal pellet M _2, and mixed The anode basket filled in the state is used. That is, for example, when the alloy plating layer formed on the metal strip 10 is a nickel-cobalt alloy plating layer, the anodes 70a to 70d are mixed in a nickel pellet and a cobalt pellet in the anode basket. It can comprise by filling in.

Alternatively, when the alloy plating layer formed on the metal strip 10 is an alloy of three or more kinds of metals (for example, an alloy of M ₁ , M ₂ , and M ₃ ), these three or more kinds of alloys are used. The anodes 70a to 70d may be configured using metal pellets corresponding to the above.

  In the present embodiment, the mixing ratio of the plurality of metal pellets used as the anodes 70a to 70d is determined as follows. That is, the anodes 70a to 70d in which the dissolution ratios of the metal pellets constituting the anodes 70a to 70d are the dissolution ratios corresponding to the weight ratios of the metals constituting the alloy plating layer formed on the metal strip 10. The total surface area ratio of each metal pellet constituting is determined, and the mixing ratio of the plurality of metal pellets used as the anodes 70a to 70d is determined based on the total surface area ratio.

As a more specific determination method of the mixing ratio of a plurality of metal pellets, the following is preferable. In the following, each metal forming the alloy plating layer formed on the metal strip 10 is M ₁ , M ₂ , M ₃ ,... M _n and each metal pellet constituting the anodes 70a to 70d is formed. An alloy plating layer formed on the metal strip 10 with a dissolution ratio (unit:%) as y (M ₁ ), y (M ₂ ), y (M ₃ ),..., Y (M _n ) the weight ratio of the metal of (in%) _{a, z (M 1), z} (M 2), z (M 3), ···, and z _{(M n).}
In the present embodiment, dissolution ratio of each metal pellets comprising the anode 70a~70d is, relative to the weight ratio of each metal constituting the alloy plating _{layer, M 1, M 2, M} 3, ··· M The total surface area ratio of each metal pellet in the anodes 70a to 70d satisfying the relationship of the following formula (1) for each of _n is obtained, and used as the anodes 70a to 70d based on the total surface area ratio of each metal pellet. The mixing ratio of a plurality of metal pellets is determined.
z (M _x ) −21 ≦ y (M _x ) ≦ z (M _x ) +21 (1)
(In the above formula (1), M _x represents M ₁ , M ₂ , M ₃ ,... M _n , respectively.)
In the present embodiment, the total surface area ratio of each metal pellet in the anodes 70a to 70d that satisfies the relationship of the above formula (1) is obtained, and the anode 70a is determined based on the total surface area ratio of each metal pellet. It is preferable to determine the mixing ratio of the plurality of metal pellets used as -70d, but it is more preferable to satisfy the relationship of the following formula (4), and to satisfy the relationship of the following formula (5). Further preferred.
z (M _x ) −11 ≦ y (M _x ) ≦ z (M _x ) +11 (4)
z (M _x ) −5 ≦ y (M _x ) ≦ z (M _x ) +5 (5)
(In the above formulas (4) and (5), M _x represents M ₁ , M ₂ , M ₃ ,... M _n , respectively.)

According to the present embodiment, by controlling as described above, M ₁ , M ₂ , M ₃ ,..., M _n consumed by the formation of the alloy plating layer on the metal strip 10 in the plating solution 30. The amount of metal ions and the amount of metal ions of M ₁ , M ₂ , M ₃ ,... M _n supplied from the anode can be made substantially the same, thereby containing in the plating solution 30. M ₁ , M ₂ , M ₃ ,... M _n metal ion ratio and content ratio can be made constant. As a result, the composition of the alloy plating formed on the metal strip 10 can be stabilized.

  Here, in this embodiment, the dissolution ratio of each metal pellet can be controlled by the total surface area ratio of each metal pellet in the anodes 70a to 70d. That is, the dissolution ratio of each metal pellet depends on the total surface area ratio of each metal pellet in the anodes 70a to 70d. Therefore, in the present embodiment, as described above, the dissolution ratio of each metal pellet is controlled by controlling the total surface area ratio of each metal pellet in the anodes 70a to 70d. The metal ion concentration in the inside is constant, and the composition of the alloy plating layer formed on the metal strip 10 is stabilized.

  The dissolution ratio of each metal pellet is the weight ratio of each metal dissolved by the anode current and can be calculated from the ion balance in the plating reaction.

Moreover, the total surface area ratio of each metal pellet is the ratio of the surface area of each metal pellet to the surface area of all metal pellets constituting the anodes 70a to 70d. That is, for example, when the anodes 70a to 70d are made of nickel pellets and cobalt pellets, the total surface area ratio of cobalt is the surface area of all nickel pellets constituting the anodes 70a to 70d. The ratio of the surface area of all cobalt pellets to the total surface area of the cobalt pellets is shown. For example, when the specific surface area of nickel pellets is S _Ni [cm ² / g] and the blending amount of nickel pellets is A _Ni [g], the surface area of all nickel pellets is represented by A _Ni × S _Ni [cm ² ]. Can do. Further, when the specific surface area of the cobalt pellet is S _Co [cm ² / g] and the blending amount of the cobalt pellet is A _Co [g], the surface area of all the cobalt pellets is represented by A _Co × S _Co [cm ² ]. Can do. Therefore, in the present embodiment, calculation is performed from the blending amount and the specific surface area so that the dissolution ratio of each metal pellet corresponds to the metal ratio (weight ratio) in the alloy plating layer formed on the metal strip 10. By controlling the total surface area ratio of each metal pellet, the metal ion concentration in the plating solution 30 can be made constant, and the composition of the alloy plating layer formed on the metal strip 10 can be stabilized. .

In this embodiment, for example, when the alloy plating layer formed on the metal strip 10 is a nickel-cobalt alloy plating layer, the weight ratio of cobalt is 40 to 60% by weight, that is, the nickel-cobalt alloy. It is preferable that z (Co), which is a weight ratio of cobalt in the plating layer (unit:%), is 40 ≦ z (Co) ≦ 60. In this case, the mixing ratio of nickel pellets and cobalt pellets The (weight ratio) is preferably as follows.
That is, the total surface area ratio (unit is%) of the cobalt pellets contained in the anodes 70a to 70d is x (Co), and the dissolution ratio (unit is%) of the cobalt pellets constituting the anodes 70a to 70d. , Y (Co), the anodes 70a to 70d are configured so that x (Co) satisfies the following expressions (2) and (3) in relation to z (Co) and y (Co). It is preferable to determine the mixing ratio of nickel pellets and cobalt pellets.
z (Co) -21 ≦ y (Co) ≦ z (Co) +21 (2)
y (Co) = − 0.8x (Co) ² /100+1.8x(Co) (3)

  Here, the total surface area ratio (unit is%) of the nickel pellets contained in the anodes 70a to 70d is x (Ni), and the dissolution ratio of nickel pellets constituting the anodes 70a to 70d (unit is%). ) Is y (Ni) and the weight ratio (unit:%) of nickel in the nickel-cobalt alloy plating layer is z (Ni), usually x (Co) + x (Ni) = 100 , Y (Co) + y (Ni) = 100, and z (Co) + z (Ni) = 100.

In this embodiment, the cobalt pellets contained in the anodes 70a to 70d have a dissolution ratio y (Co) of the cobalt pellets constituting the anodes 70a to 70d so as to satisfy the above formulas (2) and (3). By controlling the total surface area ratio x (Co), the ratio and content ratio of nickel ions and cobalt ions contained in the plating solution 30 can be made constant. As a result, the composition of the nickel-cobalt alloy plating layer formed on the metal strip 10 can be stabilized. In addition, it is more preferable to satisfy | fill following formula (6) from a viewpoint that the composition of a nickel-cobalt alloy plating layer can be made more stable, and satisfy | filling following formula (7). Is more preferable.
z (Co) -11 ≦ y (Co) ≦ z (Co) +11 (6)
z (Co) -5 ≦ y (Co) ≦ z (Co) +5 (7)

  In addition, the said Formula (2) is a relational expression which shows the relationship between the dissolution ratio y (Co) of the cobalt pellet which comprises the anodes 70a-70d, and the weight ratio z (Co) of the cobalt in an alloy plating layer, According to the knowledge of the present inventors, y (Co) is made to satisfy the above formula (2) in relation to z (Co) (more preferably, the above formula (6), more preferably the above formula). (By satisfying (7)), the ratio and content ratio of nickel ions and cobalt ions contained in the plating solution 30 are made constant, and thereby the nickel-cobalt alloy plating layer formed on the metal strip 10 It is possible to stabilize the composition.

  Further, the above formula (3) shows the relationship between the dissolution ratio y (Co) of the cobalt pellets constituting the anodes 70a to 70d and the total surface area ratio x (Co) of the cobalt pellets contained in the anodes 70a to 70d. According to the knowledge of the present inventors, when the weight ratio z (Co) of cobalt in the alloy plating layer is in the range of 40 ≦ z (Co) ≦ 60, y (Co) X (Co) satisfies the relationship of the above formula (3). Therefore, according to this embodiment, based on the above formula (2), the target dissolution ratio y (Co) of the cobalt pellet is obtained, and the obtained dissolution ratio y (Co) of the cobalt pellet is used to calculate the above formula. According to (3), the target total surface area ratio x (Co) of the cobalt pellet is determined, and based on the total surface area ratio x (Co) of the cobalt pellet, the mixing ratio of nickel pellets and cobalt pellet (weight ratio) ) Can be determined.

  For example, when the weight ratio z (Co) of cobalt in the nickel-cobalt alloy plating layer is set to z (Co) = 50 (that is, 50% by weight), dissolution of cobalt pellets constituting the anodes 70a to 70d is performed. The ratio y (Co) is preferably 29 ≦ y (Co) ≦ 71 from the above formula (2), more preferably 39 ≦ y (Co) ≦ 61 from the above formula (6), From the above formula (7), it is more preferable that 45 ≦ y (Co) ≦ 55. In this case, the total surface area ratio x (Co) of the cobalt pellets contained in the anodes 70a to 70d is 17.5 ≦ x (Co) ≦ 51.0 from the above formulas (2) and (3). From the above formulas (3) and (6), more preferably 24.3 ≦ x (Co) ≦ 41.6, and from the above formulas (3) and (7), 28.6. More preferably, ≦ x (Co) ≦ 36.5.

Thus, for example, as is clear from the specific numerical range when the weight ratio z (Co) of cobalt in the nickel-cobalt alloy plating layer is z (Co) = 50, In order to form a stable alloy plating layer, the mixing ratio (weight ratio) of the metal pellets constituting the anodes 70a to 70d does not necessarily correspond to the metal ratio (weight ratio) of the alloy plating layer. Therefore, it is necessary to have a relationship satisfying the above-described expressions. In the present embodiment, the total surface area ratio x (Co) of the cobalt pellets satisfying the above equations is obtained, and based on this, the mixing ratio of nickel pellets and cobalt pellets constituting the anodes 70a to 70d ( Weight ratio). In addition, as a method of calculating | requiring the mixing ratio (weight ratio) of a nickel pellet and a cobalt pellet from the total surface area ratio x (Co) of a cobalt pellet, the method of using the value of the surface area per weight of a nickel pellet and a cobalt pellet, for example Etc.
In the above description, the case where a nickel-cobalt alloy plating layer is formed on the metal strip 10 is mainly described as an example. However, the present invention is not limited to such an embodiment.

  In the present embodiment, the shape and mixing ratio of the plurality of metal pellets used as the anodes 70a to 70d may be within the above-described range, but the plurality of metal pellets used as the anodes 70a to 70d are usually plated. It is inevitable that it will dissolve and wear out as the process proceeds.

  In particular, the density of each metal pellet is not greatly different, and when the target dissolution ratio is 1: 1, each metal pellet has the same shape and the same size. Since fluctuations in the total surface area ratio can also be suppressed, it is possible to form a stable alloy plating layer. Therefore, the same shape and the same size are desirable. However, on the other hand, when it is difficult to obtain metal pellets of the same shape and the same size, or when the density of the metal constituting each metal pellet is different, and when the target dissolution ratio is not 1: 1, It is not always necessary to use metal pellets having the same shape and size, and it is desirable to select and use pellets having a shape, shape and size that can reduce the change in the total surface area ratio of each metal pellet due to wear. In particular, by adjusting the shape and size of each metal pellet, the surface area change due to wear per metal pellet can be predicted even if it is not necessarily the same shape and size. However, if it synchronizes between each metal pellet, the fluctuation | variation of the total surface area ratio of each metal pellet accompanying consumption can be suppressed effectively, and, thereby, a stable alloy plating layer can be formed.

  In addition, in the present embodiment, in addition to the above method, as described later, in order to supplement the consumed metal pellets, it is already consumed by replenishing each genus pellet periodically at a predetermined ratio. Variations in the total surface area ratio of each metal pellet due to the influence of the metal pellet can be suppressed.

Moreover, in this embodiment, when forming an alloy plating layer on the metal strip 10, the current density at the time of electroplating is 1-40A / from the point of stabilizing the composition of the formed alloy plating layer. dm ² is preferable, and the pH of the plating solution 30 is preferably 1.5 to 5. Moreover, it is preferable to make the temperature (bath temperature) of the plating solution 30 into 40-80 degreeC. If the current density during electroplating is too large or too small, the pH of the plating solution 30 is too high or too low, and the temperature of the plating solution 30 is too high. However, even if it is too low, the composition of the formed alloy plating layer may become unstable.

  Furthermore, in the present embodiment, as each metal pellet is dissolved and consumed as the plating process proceeds, it is preferable to regularly replenish each metal pellet in the anode basket. In addition, the replenishment ratio of each metal pellet when replenishing each metal pellet is not particularly limited, but is preferably a ratio corresponding to the weight ratio of each metal constituting the alloy plating layer. For example, when the alloy plating layer formed on the metal strip 10 is a nickel-cobalt alloy plating layer having a cobalt content of 50% by weight, the ratio of each metal pellet to be replenished is “nickel pellet: cobalt pellet. The weight ratio may be 1: 1. In particular, since each metal pellet in the anodes 70a to 70d is dissolved at a weight ratio according to the composition ratio of the alloy plating layer to be formed, in this embodiment, when replenishing the metal pellet, It is desirable to replenish at a ratio corresponding to the weight ratio of each metal constituting the alloy plating layer, and this makes it possible to stably form the alloy plating layer. In the present embodiment, when replenishing the metal pellets, the metal pellets may be replenished at a ratio corresponding to the weight ratio of each metal constituting the alloy plating layer as described above. Even when depleted, the metal pellets can be replenished more easily.

  The timing for replenishing the metal pellet is not particularly limited, but when the metal pellet is dissolved and the total surface area is reduced, that is, when the surface area of all the metal pellets constituting the anodes 70a to 70d is reduced, Since the anode or cathode current density deviates from the set range, it is desirable to replenish the pellets continuously.

Further, in the present embodiment, the metal pellets used for the anodes 70a to 70d are not particularly limited, but the representative length (in the case of a spherical shape, means the diameter thereof, and in the case of other shapes, It is preferable to use one having a maximum length in the shape of 5 to 50 mm (preferably 5 to 40 mm) and a volume of 60 to 5000 mm ³ . According to this embodiment, by using pellets of such a representative length and volume, when replenishing metal pellets, the metal pellets are continuously added at a desired weight ratio while stabilizing the total surface area without significant change. It is possible to replenish, and it is possible to suppress the fluctuation of the total surface area of each metal pellet by making it possible to suppress the fluctuation of the specific surface area due to wear and suppress the fluctuation of the total surface area ratio of each metal pellet. it can. Furthermore, by using pellets of such representative length and volume, fluctuations in the total surface area ratio of each metal pellet due to the influence of metal pellets that have already been consumed due to the metal pellets added during replenishment can be suppressed. , Sufficient stability can be obtained.

  In particular, if the representative length of the metal pellet is too large, the weight and area per metal pellet will increase, so the total surface area will change significantly when the metal pellet is added by replenishment, and the total surface area will be stable. It becomes difficult. Furthermore, especially when metal pellets of different sizes are used for each metal, as described above, when the metal pellets are replenished at a weight ratio, the total surface area ratio of each metal pellet is likely to change. Therefore, it is not preferable. On the other hand, the present inventors have conducted intensive studies in consideration of the industrially available plating speed, the size of the anode basket, the size of the metal strip 10 to be plated, and the size of the equipment. The present invention has been found to suppress changes in the total surface area and the total surface area ratio of each metal pellet due to replenishment by using a metal pellet having a representative length and volume within the above range. From the viewpoint of suppressing changes in the total surface area and the total surface area ratio of each metal pellet due to replenishment, in the present embodiment, it is preferable to use a metal pellet having a representative length and volume within the above ranges.

  On the other hand, if the size of the metal pellet to be used, that is, the volume (the initial size that has not been consumed) is too large, the specific surface area between the initial metal pellet that has not been consumed and the metal pellet that has been consumed As a result, the variation in the total surface area ratio of each metal pellet due to wear is significantly increased. As a result, the composition of the formed alloy plating layer becomes unstable, which is not preferable. On the other hand, if the representative length of the metal pellet is too large, it is difficult to fill the anode basket without a gap, the filling rate is lowered, and there is a possibility that a void without the pellet is generated. Moreover, there exists a possibility that the solubility to the plating solution 30 may fall.

  On the other hand, if the representative length is too small or the volume is too small, the pellets will bounce or fall when filling the anode basket, making handling difficult and coming out of the anode basket. There is a risk of clogging between the anode basket and the anode bag installed outside the anode basket, resulting in a protruding shape. If the representative length is too large, it is difficult to fill the anode basket without a gap, and the filling rate is lowered, and there is a possibility that a void without pellets is generated. Moreover, there exists a possibility that the solubility to the plating solution 30 may fall.

On the other hand, by using a metal pellet having a representative length of 5 to 50 mm and a volume of 60 to 5000 mm ³ , the total surface area can be replenished continuously in a weight ratio while stabilizing without significant change during replenishment. In addition, it is possible to suppress the variation in the total surface area ratio of each metal pellet by enabling the variation in the specific surface area due to wear to be suppressed. Furthermore, by using metal pellets having such a representative length and volume, the fluctuation of the total surface area ratio of each metal pellet due to the influence of metal pellets that have already been consumed by the metal pellets added during replenishment is suppressed. Can obtain sufficient stability

  Moreover, in this embodiment, it does not specifically limit as a shape of the metal pellet used for anode 70a-70d, For example, a spherical shape, an ellipsoid, a cylindrical shape, a coin shape, or the shape close | similar to these is used preferably. In particular, by using such a shape, even if the anodes 70a to 70d are filled and consumed (dissolved) and become smaller as the electroplating progresses, Since the shape can be maintained, and even when the melting proceeds further, it eventually approaches a spherical shape, so it is easy to calculate or predict the total surface area ratio of each metal pellet due to wear, so the total surface area of each metal pellet There is an advantage that the ratio is easy to stabilize.

  Moreover, in this embodiment, in order to adjust the density | concentration of a plating solution, you may add a metal salt compound powder suitably. In addition, as for the addition amount of metal salt compound powder, it is desirable to set suitably in the range which does not impair the effect of this invention.

  In this embodiment, when forming an alloy plating layer by electroplating the metal strip 10, two or more kinds of metal pellets for forming the alloy plating layer are mixed as the anodes (anodes) 70a to 70d. An anode is used. Therefore, according to this embodiment, the fluctuation | variation of the metal ion concentration in the plating solution contained in a plating tank can be suppressed, and, thereby, an alloy plating layer can be stably formed on the metal strip 10. it can. In particular, according to the present embodiment, for example, there is no problem that the counter anion increases as in the method of adding the metal salt compound powder to the plating solution and dissolving it in the plating solution. It is possible to effectively prevent the problems associated with the above, that is, the problem that the plating film having the intended composition and characteristics cannot be stably obtained.

  In addition, according to the present embodiment, the dissolution ratio of the anode can be set finely by changing the blending ratio of the metal pellets for forming the alloy plating layer. The composition can be selected in detail from a wide composition range.

  In particular, the case of forming a nickel-cobalt alloy plating layer is exemplified. In the method using a nickel electrode and a cobalt electrode as an anode and using these as a supply source of nickel ions and cobalt ions, the following problems are caused. There is.

  That is, for example, as in the example shown in FIG. 2, in the plating line shown in FIG. 1, the anodes 70a and 70d constituting the plating line are nickel electrodes, the anodes 70b and 70c are cobalt electrodes, and nickel and cobalt In order to form a nickel-cobalt alloy plating layer having a molar ratio of 1: 1, when a current of 1000 A is passed through each of the anodes 70a to 70d, one surface (the anode 70a) , 70d), the formed alloy layer has a nickel-rich composition, and on the other surface (the face close to the anodes 70b, 70c), the formed alloy layer has a cobalt-rich composition. Variations in composition occur.

  Alternatively, like the example shown in FIG. 3, similarly to the example shown in FIG. 2, nickel-cobalt alloy plating that constitutes each of the anodes 70 a to 70 d and has a molar ratio of nickel to cobalt of 2: 1. In order to form a layer, when the current flowing through the anodes 70a and 70d is 1333A and the current flowing through the anodes 70b and 70c is 666A, as in the example shown in FIG. The surface of the alloy layer formed near the anodes 70a and 70d has a nickel-rich composition, and the other layer (the surface close to the anodes 70b and 70c) has a cobalt-rich composition. As a result, variation in composition occurs. In addition, in the example shown in FIG. 3, the ratio between the thickness of the alloy layer on the surface close to the anodes 70a and 70d and the thickness of the alloy layer on the surface close to the anodes 70b and 70c depends on the amount of current. Since the thickness, that is, the inconvenience of the ratio of 2: 1 and the current density are different, there is a possibility that the film having the desired characteristics cannot be obtained.

  Further, as in the example shown in FIG. 4, the anodes 70b and 70d constituting the plating line are made of nickel electrodes, and the anodes 70a and 70c are made of cobalt electrodes. Similarly to the example shown in FIG. When a nickel-cobalt alloy plating layer having a molar ratio of 2: 1 is formed, unlike the case of FIG. 3, the thickness of the alloy layer on the surface adjacent to the anodes 70a and 70d, and the anodes 70b and 70c. Although the ratio with the thickness of the alloy layer on the surface close to the surface can be made uniform, the problem of composition variation still cannot be solved, and even in this case, the current density is different. Therefore, there is a possibility that a film having the desired characteristics cannot be obtained.

  In addition, in the example shown in FIGS. 2 to 4, since the amount of current supplied to each of the anodes 70 a to 70 d needs to be controlled for each of the anodes 70 a to 70 d, unlike the example shown in FIG. It is necessary to use a rectifier for each of the anodes 70a to 70d (that is, four rectifiers are required in the example shown in FIGS. 2 to 4), and the manufacturing cost is higher than the example shown in FIG. There is a problem of becoming.

  For example, when the number of rectifiers is two in the example illustrated in FIG. 4 as in the example illustrated in FIG. 5, for example, the anodes 70 a and 70 d are illustrated as an example. Even if an attempt is made to pass a current evenly by 1000 A, the current cannot be caused to flow uniformly by 1000 A due to the influence of the resistance of the current line reaching each anode, and therefore the composition of the resulting alloy layer is appropriately controlled. There is a bug that can not be.

  On the other hand, according to the present embodiment, the dissolution ratio of the anode can be finely set by changing the blending ratio of the metal pellets for forming the alloy plating layer, and supplied from each anode. Since the ratio of metal ions can be made uniform, it is possible to effectively prevent the occurrence of problems as shown in FIGS.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
First, a steel strip (thickness 0.2 mm, width 200 mm) having the chemical composition shown below was prepared.
C: 0.039 wt%, Mn: 0.02 wt%, Si: 0.22 wt%, P: 0.016 wt%, S: 0.008 wt%, balance: Fe and inevitable impurities

  The prepared steel strip is electrolytically degreased, washed with water, pickled with sulfuric acid, further washed with water, and then continuously plated with nickel-cobalt alloy on the surface of the steel strip using the plating line shown in FIG. The ratio of “nickel: cobalt” is 50:50 (weight ratio), that is, the weight ratio z (Co) of cobalt in the alloy plating layer is z (Co). = 50 A nickel-cobalt alloy plating layer was continuously formed. The ratio of “nickel: cobalt” is obtained by forming the nickel-cobalt alloy plating layer, dissolving the formed nickel-cobalt alloy plating layer, and performing ICP emission spectroscopic analysis on the obtained melt. It was measured.

Specifically, the nickel-cobalt alloy plating layer is continuously formed under the conditions of a current density of each anode 70a to 70d: 10 A / dm ² and a plating treatment time: 8 hours while stirring 2 L of the plating solution 30. Processing to form was performed.

As anodes 70a to 70d, spherical nickel pellets (specific surface area: 0.6 cm ² / g, diameter: 10.7 mm) 1469 g and coin-shaped cobalt pellets (specific surface area: 0.6 cm ² / g, thickness) The diameter of the surface perpendicular to the direction: 34.0 mm) was mixed with 733 g, and these were filled in an anode basket. That is, an anode having nickel pellets (x (Ni)): cobalt pellets (x (Co)) = 66.7: 33.3 (surface area ratio) was used.

In this example, the following plating solution was used as the plating solution 30.
Bath composition: Nickel sulfate, nickel chloride, cobalt sulfate, cobalt chloride, and boric acid are contained at nickel ion concentration: 65.4 g / L, cobalt ion concentration: 12.6 g / L pH: 3.5 to 5.0
Bath temperature: 60 ° C

  In this example, the stability of the plating solution composition was evaluated by measuring the nickel ion concentration and the cobalt ion concentration in the plating solution every hour during the plating process for 8 hours. FIG. 6A shows the measurement results of the nickel ion concentration and the cobalt ion concentration during the plating process for 8 hours.

Example 2
As anodes 70a to 70d, spherical nickel pellets (specific surface area: 0.6 cm ² / g, diameter: 10.7 mm) 974 g and coin-shaped cobalt pellets (specific surface area: 0.6 cm ² / g, perpendicular to the thickness direction) The surface was mixed with 985 g and the anode basket was filled (nickel pellet (x (Ni)): cobalt pellet (x (Co))) = 49.7: 50 .3 (surface area ratio)) In the same manner as in Example 1, the steel strip was electroplated to continuously form a nickel-cobalt alloy plating layer. FIG. 6B shows the measurement results of the nickel ion concentration and the cobalt ion concentration during the plating process for 8 hours.

Example 3
As anodes 70a to 70d, spherical nickel pellets (specific surface area: 0.6 cm ² / g, diameter: 10.7 mm) 1684 g, coin-shaped cobalt pellets (specific surface area: 0.6 cm ² / g, perpendicular to the thickness direction) (Nickel pellet (x (Ni)): Cobalt pellet (x (Co))) = 75.1: 24 .9 (surface area ratio)) In the same manner as in Example 1, the steel strip was electroplated to continuously form a nickel-cobalt alloy plating layer. In Example 3, the plating treatment time was changed from 8 hours to 6 hours. FIG. 6C shows the measurement results of the nickel ion concentration and the cobalt ion concentration during the plating process for 6 hours.

<< Comparative Example 1 >>
As anodes 70a to 70d, except that a spherical nickel pellet (specific surface area: 0.6 cm ² / g, diameter: 10.7 mm) 2222 g was filled in an anode basket, the same as in Example 1, The steel strip was electroplated to continuously form a nickel-cobalt alloy plating layer. FIG. 7A shows the measurement results of the nickel ion concentration and the cobalt ion concentration during the plating process for 8 hours.

<< Comparative Example 2 >>
As anodes 70a to 70d, except that coin-type cobalt pellets (specific surface area: 0.6 cm ² / g, diameter of surface perpendicular to the thickness direction: 34.0 mm) 1738 g only filled in an anode basket were used. In the same manner as in Example 1, the steel strip was electroplated to continuously form a nickel-cobalt alloy plating layer. FIG. 7B shows the measurement results of the nickel ion concentration and the cobalt ion concentration during the 8-hour plating process.

<Evaluation>
As shown in FIG. 6 (A) to FIG. 6 (C), in Examples 1 to 3 using the anodes 70a to 70d, which were prepared by mixing nickel pellets and cobalt pellets and filling the anode basket. Fluctuation of nickel ion concentration and cobalt ion concentration during 8 hours (or 6 hours) of plating treatment can be appropriately suppressed, thereby stabilizing the composition of the nickel-cobalt alloy plating layer formed on the steel strip. It was possible to make it. In particular, in Example 1 in which the anodes 70a to 70d were anodes having nickel pellets (x (Ni)): cobalt pellets (x (Co)) = 66.7: 33.3 (surface area ratio), The nickel ion concentration and the cobalt ion concentration during the plating process for a long time can be made constant, and the composition of the nickel-cobalt alloy plating layer formed on the steel strip can be made almost uniform. .

  On the other hand, as shown in FIGS. 7 (A) to 7 (B), in Comparative Example 1 using only nickel pellets and Comparative Example 2 using only cobalt pellets as anodes 70a to 70d, plating was performed for 8 hours. During the treatment, the nickel ion concentration and the cobalt ion concentration fluctuated greatly, and as a result, the composition of the nickel-cobalt alloy plating layer formed on the steel strip also fluctuated.

FIG. 8 shows the relationship between the cobalt ratio (area ratio) in the anodes 70a to 70d and the cobalt dissolution ratio (weight ratio) calculated from the ion balance in Examples 1 to 3 and Comparative Examples 1 and 2. . As shown in FIG. 8, when the cobalt mixing ratio in the anode increases (when the nickel mixing ratio decreases), the cobalt dissolution ratio of the anodes 70a to 70d tends to increase (the nickel dissolution ratio decreases). Can be confirmed to have a certain relationship (y (Co) = − 0.8x (Co) ² /100+1.8x(Co)).

In Table 1, the total surface area ratio x (Co) of cobalt pellets in the anodes 70a to 70d, the dissolution ratio y (Co) of cobalt pellets, and the plating solution in Examples 1 to 3 and Comparative Examples 1 and 2 The relationship with the evaluation result of stability is shown. In Table 1, the stability of the plating solution was evaluated according to the following criteria. That is, based on the fluctuation width within 6 hours of each metal ion concentration (g / L) constituting the plating solution (that is, the difference between the maximum value and the minimum value within 6 hours), the following criteria were evaluated. . It can be evaluated that the smaller the swing width, the more excellent the stability of the plating solution.
A: The runout is within 5 g / L, and the deviation from the initial value is within ± 3.5 g / L.
B: The swing width is within 5 g / L, and the deviation from the initial value exceeds ± 3.5 g / L. C: The swing width is within 8 g / L.
D: The runout is over 8 g / L.

  As is apparent from the results in Table 1, it can be confirmed that Examples 1 to 3, particularly Examples 1 and 3, are excellent in the stability of the plating solution.

DESCRIPTION OF SYMBOLS 10 ... Metal strip 20 ... Plating tank 30 ... Plating solution 40, 60 ... Conductor roll 50 ... Sink roll 70a, 70b, 70c, 70d ... Anode 80a, 80b ... Rectifier

Claims (5)

A method of manufacturing a metal plate having an alloy plating layer,
A step of performing electroplating in the plating tank by continuously passing a metal strip in a plating tank comprising a plating solution containing two or more kinds of metal ions for forming the alloy plating layer and an anode. Prepared,
Using an anode obtained by mixing two or more metal pellets made of each metal forming the alloy plating layer as the anode,
Based on the total surface area ratio of each metal pellet in the anode, such that the dissolution ratio of each metal pellet constituting the anode is a dissolution ratio corresponding to the weight ratio of each metal constituting the alloy plating layer, Determine the mixing ratio of each metal pellet constituting the anode ,
A ratio corresponding to the weight ratio of each metal constituting the alloy plating layer, the replenishment ratio of the metal pellets when replenishing the metal pellets in the anode when performing electroplating in the plating tank method for producing a metal plate having an alloy plated layer, characterized in that a. Each metal forming the alloy plating layer is M ₁ , M ₂ , M ₃ ,... M _n, and the dissolution ratio (unit:%) of each metal pellet constituting the anode is y (M ₁ ), Y (M ₂ ), y (M ₃ ),..., Y (M _n ), and the weight ratio (unit:%) of each metal constituting the alloy plating layer is z (M ₁ ). , Z (M ₂ ), z (M ₃ ),..., Z (M _n )
The dissolution ratio of each metal pellet constituting the anode is _{expressed by} the following formula (1) for each of M ₁ , M ₂ , M ₃ ,... M _n with respect to the weight ratio of each metal constituting the alloy plating layer. 2. The alloy plating according to claim 1, wherein a mixing ratio of each metal pellet constituting the anode is determined based on a total surface area ratio of each metal pellet in the anode so as to satisfy the relationship of A method for producing a metal plate having a layer.
z (M _x ) −21 ≦ y (M _x ) ≦ z (M _x ) +21 (1)
(In the above formula (1), M _x represents M ₁ , M ₂ , M ₃ ,... M _n , respectively.) Examples Each metal pellets, characteristic length is 5 to 50 mm, and volume of the metal plate having the alloy plating layer according to claim 1 or 2, characterized in that used as a 60～5000Mm ³ Production method. The alloy plating layer is a nickel-cobalt alloy plating layer,
The method for producing a metal plate having an alloy plating layer according to any one of claims 1 to 3 , wherein the anode is an anode obtained by mixing nickel pellets and cobalt pellets. Z (Co) which is a weight ratio (unit:%) of cobalt in the alloy plating layer is set to 40 ≦ z (Co) ≦ 60,
X (Co) which is a total surface area ratio (unit:%) of the cobalt pellet is y (Co) which is a dissolution ratio (unit:%) of the cobalt pellet constituting the z (Co) and the anode. 5. The alloy plating according to claim 4 , wherein a mixing ratio of the nickel pellets and the cobalt pellets constituting the anode is determined so as to satisfy the following formulas (2) and (3): A method for producing a metal plate having a layer.
z (Co) -21 ≦ y (Co) ≦ z (Co) +21 (2)
y (Co) = − 0.8x (Co) ² /100+1.8x(Co) (3)

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